Method for automatic load compensation for a cobot or an upper limb exoskeleton

Abstract

A control method for controlling an actuator (11) connected to a load (50) for handling, the method comprising the steps of:detecting an intention to handle the load (50);applying an increasing command to the actuator (11) until detecting a movement of the actuator (11);storing the value reached by the command when a movement of the actuator (11) is detected;using the stored value reached by the command to determine an estimate of the opposing force exerted by the load (50) for handling; andcontrolling the actuator by means of a force servocontrol relationship using the estimate of the opposing force exerted by the load (50) for handling in order to establish the commands to be applied to the actuator (11).A cobot (1) arranged to perform the method.

The invention claimed is: 
     
       1. A control method for controlling an actuator of a cobot, the actuator being functionally connected to a load for handling and being controlled by a monitor and control unit, the method comprising the steps of:
 detecting an intention of a user of the cobot to handle the load for handling; 
 
       when the user and/or the cobot handle the load, applying an increasing command value to the actuator, seeking to cause the load for handling to move until detecting a movement of the actuator or of the load for handling or until detecting that the intention to handle the load for handling has ceased;
 storing the value reached by the command and/or by a sensor linked to the actuator when a movement of the actuator or of the load for handling is detected or when detecting that the intention to handle the load for handling has ceased; 
 using the stored value reached by the command and/or by the sensor linked to the actuator to determine an estimate of the opposing force exerted by the load for handling; and 
 controlling the actuator by means of a force servocontrol relationship using the estimate of the opposing force exerted by the load for handling in order to establish the commands to be applied to the actuator, 
 resetting the value of the estimate of the opposing force exerted by the load for handling to zero when the intention to handle the load ceases to be detected. 
 
     
     
       2. A control method according to  claim 1 , wherein the increasing command results from a non-zero speed setpoint applied by the monitor and control unit. 
     
     
       3. A control method according to  claim 1 , wherein the increasing command comprises an increasing force command applied by the monitor and control unit. 
     
     
       4. A control method according to  claim 3 , wherein the increasing force command comprises a torque command. 
     
     
       5. A control method according to  claim 1 , wherein the estimate of the opposing force of the load for handling is determined by using the value taken by a sensor for sensing the current of the actuator when a movement of the actuator is detected. 
     
     
       6. A control method according to  claim 1 , wherein the estimate of the opposing force of the load for handling is determined by using the value taken by a current setpoint being sent to the actuator when a movement of the actuator is detected. 
     
     
       7. A control method according to  claim 1 , wherein the step of detecting a movement of the actuator comprises a step of detecting the crossing of a speed threshold or the crossing of a movement threshold or the crossing of an acceleration threshold. 
     
     
       8. A control method according to  claim 1 , wherein the step of detecting an intention to handle the load for handling comprises a step of detecting a change of state of an intention sensor. 
     
     
       9. A control method according to  claim 8 , wherein the intention sensor comprises a dry contact. 
     
     
       10. A control method according to  claim 8 , wherein the intention sensor is positioned on a hand of a user of the actuator. 
     
     
       11. A control method according to  claim 8 , wherein the intention sensor comprises a pressure sensor and/or an attitude sensor and/or an acceleration sensor and/or a flexion sensor and/or a myoelectrical sensor. 
     
     
       12. A cobot including a monitor and control unit connected to an actuator, the cobot also including detector means for detecting an intention of a user of the cobot to handle a load and/or a sensor linked to the actuator and linked to the monitor and control unit, the cobot being arranged to perform the method according to  claim 1 . 
     
     
       13. A cobot according to  claim 12 , wherein the detector means for detecting an intention to handle a load also include an intention sensor, the control unit being arranged to detect an intention to handle the load for handling comprises a step of detecting a change of state of an intention sensor. 
     
     
       14. The control method according to  claim 1 , wherein the command value controls a torque of the actuator. 
     
     
       15. The control method according to  claim 1 , wherein the command value controls a force of the actuator.